Compound 1, Palbociclib (6-acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-Pyrido[2,3-d]pyrimidin-7-one) is a drug approved by the US FDA and is an oral inhibitor of cyclin-dependent kinase 4, 6 (CDK4/6). There is a precise program named cell cycle regulation mechanism that regulates cell growth, proliferation, or death in every living individual. The disruption of cell cycle regulation mechanisms leads to uncontrolled growth of cells, a common feature of almost all tumor development. In the mammalian cell cycle, the regulation point from the G1 phase to the S phase, the R point (Restriction point), is a key point in the regulation of cell proliferation. Only the breakthrough of the R point, DNA replication in S phase can be triggered for cell proliferation. The regulation of this point is closely related to the occurrence and development of tumors. Palbociclib can target the G1 phase of the cell cycle and block the proliferation of cancer cells. Palbociclib is used in patients with advanced breast cancer who are estrogen receptor (ER) positive, human epidermal growth factor receptor-2 (HER2) negative, and postmenopausal women.
Palbociclib has a molecular Formula of C24H29N7O2 and a molecular weight of 447.53. The chemical structure of Palbociclib (Compound 1) is as follows:

Chemical raw materials of active pharmaceutical ingredients (API) must have good purity, stability, physical and chemical properties and operability. These properties are related to the crystalline Form of the drug, and different crystal Forms have different physical and chemical properties. The purpose of improving the stability of the drug preservation and the efficacy of the drug, it is necessary to make the raw API into crystal Form.
A drug may exist in a plurality of crystalline Forms, and different crystal Forms of the same drug may have different dissolution and absorption in the body, thereby affecting the dissolution and release of the Formulation.
The optimal crystalline Form can be discovered by thoroughly studying of the polymorphism of the compound. The optimal crystalline Form is crucial to the efficacy of the drug and the Formulation process which is based on the characteristics of the crystalline Form, thereby effectively ensuring the equivalence of the drug batch to batch.
However, in the prior art, the solubility of Palbociclib in crystal Forms A and B in water is very small, which is detrimental to the dissolution and release of the drug, resulting in a decrease in bioavailability and a food effect.